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Abstract

South Central Minnesota has experienced frequent flooding in the past because of the relatively flat topography, low elevation, and large amounts of snow melt in the spring. When these events happen, there is a large economic impact and potential health hazards to residents of the area. Having up-to-date flood zone maps can help residents be better prepared for emergency situations. Using Geographic Information Science (GIS), flood zone maps can be updated frequently in a more time efficient and inexpensive manner. Using a 30-meter digital elevation model (DEM) Compound Topographic Index (CTI) and Stream Power Index (SPI) layers were calculated for the all of South Central Minnesota for this study. These two indices combined were used to identify areas that would be more prone to flooding. 30-meter, 10-meter, and 3-meter resolution DEMs were used to create CTI and SPI layers for analysis in the Seven Mile Creek Watershed. They were used to not only find areas prone to flooding but also to find how the resolution of the DEM affects the outcomes of the indices. Also, flood levels were created for the city of Mankato, MN using a DEM cell selection process. These flood levels were used to identify land and buildings that could be inundated in the event of flood water breaching the levee. The costs of such damages were also calculated using parcel shapefiles and lidar-derived building footprints. The role of the DEM was also examined during the creation of these flood levels. Using 30-meter, 10-meter, and 1-meter resolution DEMs, the differences in the total extent of each flood stage and the predicted financial impacts were examined.